使用2D对象数组java的NPE
我在这个代码中得到了一个NPE。我试图初始化每个索引,但似乎也不起作用。你能指出什么地方不对吗?谢谢使用2D对象数组java的NPE,java,nullpointerexception,Java,Nullpointerexception,我在这个代码中得到了一个NPE。我试图初始化每个索引,但似乎也不起作用。你能指出什么地方不对吗?谢谢 package com.js.teachEnglish; import java.awt.FlowLayout; import java.awt.Font; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.io
package com.js.teachEnglish;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileReader;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
public class Piggy_Panel extends JPanel {
/**
*
*/
private static final long serialVersionUID = 1L;
int number_lines = getLines(Helper.piggybackResource.getPath());
protected JLabel title_Label = new JLabel("Piggyback words");
protected ImageIcon button_image = new ImageIcon(Helper.soundIconResource);
protected JButton title_Button = new JButton(button_image);
protected JPanel titlePanel = new JPanel();
protected JScrollPane pane = new JScrollPane(this);
protected JLabel[] label_group = new JLabel[number_lines];
protected JButton[] button_group = new JButton[number_lines];
protected String[] information = new String[number_lines];
// Table information
protected String[] col_titles = new String[] {"",""};
protected Object[][] table_contents = new Object[number_lines][];
protected JTable table;
// constructor
public Piggy_Panel() {
setLayout(new GridLayout(number_lines+1,1));
// scroll pane
pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// getting the information
readInformation();
/*
* adding the title seperately
* and also adding characteristics for the label
* */
titlePanel = new JPanel();
titlePanel.setLayout(new FlowLayout());
// adding the characteristics for the label
title_Label.setFont(new Font("Arial",Font.PLAIN,36));
titlePanel.add(title_Label);
titlePanel.add(title_Button);
add(titlePanel);
// calling the ini_labels_buttons() to initlialise the buttons and labels
ini_labels_buttons();
// fill the object[][] in
fill_table();
// initialising table and adding specific characteristics
table = new JTable(table_contents, col_titles);
table.setFillsViewportHeight(true);
table.setShowHorizontalLines(false);
table.setShowVerticalLines(false);
add(table);
// calling the ini_panel_group() to add everything
title_Button.addActionListener(new buttonListener());
}
// will read the information from the file
public String[] readInformation() {
try {
String line = null;
BufferedReader br = new BufferedReader(new FileReader(Helper.piggybackResource.getPath()));
int i = 0;
while((line = br.readLine()) != null) {
information[i] = line;
i++;
}
return information;
}catch(Exception ex) {
ex.printStackTrace();
}
return null;
}
// will put out the sound
// This will output the sound if a button is clicked
class buttonListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
JButton button = (JButton) e.getSource();
String sayDynamicPath = Helper.sayDynamicResource.getPath() + " ";
if(button.equals(title_Button)) {
try {
Runtime.getRuntime().exec(sayDynamicPath +
title_Label.getText());
}catch(Exception ex) {
JOptionPane.showMessageDialog(null,""+ex,"Unable to produce sound",
JOptionPane.ERROR_MESSAGE);
ex.printStackTrace();
}
}
}
}
// Initialising the JLabels and JButtons and also adding the relevant functions
// these include icons and information
public void ini_labels_buttons() {
// initialising the buttons first
for (int i = 0; i < button_group.length; i++) {
button_group[i] = new JButton(button_image);
}
// initialising the labels
for (int i = 0; i < label_group.length; i++) {
label_group[i] = new JLabel(information[i]);
}
}
public void fill_table() {
// fill in the first col
for (int i = 0; i < table_contents.length; i++) {
table_contents[i][0] = information[i]; // null pointer here
}
// fill in the second the col
for(int j = 0;j < table_contents.length;j++) {
table_contents[j][1] = button_group[j];
}
}
// this method will get the number of lines and then send it back
// to the label group
public int getLines(String path) {
int n = 0;
try {
BufferedReader br = new BufferedReader(new FileReader(path));
@SuppressWarnings("unused")
String line = "";
while((line = br.readLine()) != null) {
n++;
}
}catch(Exception e) {
e.printStackTrace();
}
return n;
}
}
package com.js.teachEnglish;
导入java.awt.FlowLayout;
导入java.awt.Font;
导入java.awt.GridLayout;
导入java.awt.event.ActionEvent;
导入java.awt.event.ActionListener;
导入java.io.BufferedReader;
导入java.io.FileReader;
导入javax.swing.ImageIcon;
导入javax.swing.JButton;
导入javax.swing.JLabel;
导入javax.swing.JOptionPane;
导入javax.swing.JPanel;
导入javax.swing.JScrollPane;
导入javax.swing.JTable;
公共类Piggy_面板扩展JPanel{
/**
*
*/
私有静态最终长serialVersionUID=1L;
int number_line=getline(Helper.piggybackResource.getPath());
受保护的JLabel title_Label=新JLabel(“背驮单词”);
受保护的ImageIcon按钮\u image=新的ImageIcon(Helper.soundIconResource);
受保护的JButton title_Button=新JButton(按钮图片);
受保护的JPanel titlePanel=新的JPanel();
受保护的JScrollPane=新的JScrollPane(此);
受保护的JLabel[]标签组=新的JLabel[行数];
受保护的按钮[]按钮组=新的按钮[行数];
受保护字符串[]信息=新字符串[行数];
//表信息
受保护字符串[]列标题=新字符串[]{“”“”};
受保护对象[]表内容=新对象[行数][];
保护JTable表;
//建造师
公共小猪小组(){
setLayout(新网格布局(线数+1,1));
//滚动窗格
setHorizontalScrollBarPolicy(JScrollPane.HorizontalScrollBar\uAlways);
设置垂直滚动条策略(JScrollPane.VERTICAL\u滚动条总是);
//获取信息
阅读信息();
/*
*分别添加标题
*以及为标签添加特征
* */
titlePanel=新的JPanel();
titlePanel.setLayout(新的FlowLayout());
//添加标签的特征
title_Label.setFont(新字体(“Arial”,普通字体,36));
标题面板添加(标题标签);
标题面板添加(标题按钮);
添加(标题板);
//调用ini_labels_buttons()初始化按钮和标签
ini_标签_按钮();
//将对象[]填入
填写表格();
//初始化表格并添加特定特征
表=新的JTable(表内容、列标题);
表.setFillsViewPerthweight(真);
表.设置显示水平线(假);
表1.设置显示(假);
增加(表);
//调用ini_panel_group()添加所有内容
title_Button.addActionListener(新按钮Listener());
}
//将从文件中读取信息
公共字符串[]读取信息(){
试一试{
字符串行=null;
BufferedReader br=new BufferedReader(新文件阅读器(Helper.piggybackResource.getPath());
int i=0;
而((line=br.readLine())!=null){
信息[i]=行;
i++;
}
返回信息;
}捕获(例外情况除外){
例如printStackTrace();
}
返回null;
}
//将发出声音
//如果单击按钮,将输出声音
类buttonListener实现ActionListener{
已执行的公共无效操作(操作事件e){
JButton按钮=(JButton)e.getSource();
字符串sayDynamicPath=Helper.SayDynamicSource.getPath()+“”;
如果(按钮等于(标题按钮)){
试一试{
Runtime.getRuntime().exec(sayDynamicPath+
title_Label.getText());
}捕获(例外情况除外){
showMessageDialog(null,“+ex,”“无法产生声音”,
JOptionPane.ERROR\u消息);
例如printStackTrace();
}
}
}
}
//初始化JLabel和JButtons并添加相关函数
//这些包括图标和信息
公共无效ini_标签_按钮(){
//首先初始化按钮
对于(int i=0;i
在NPE的堆栈跟踪处放血会很有用
这将创建对数组的引用数组,而不是数组数组
protected Object[][] table_contents = new Object[number_lines][];
这意味着
table_contents[i][0] = information[i];
应该抛出一个NPE,因为表内容[i]将null
。查看调试器将确认这一点
最简单的解决方案是创建一个或多个具有
protected Object[][] table_contents = new Object[number_lines][2];
顺便说一句,我会使用一个循环,而不是两个。张贴获得NPE的行。如果你有一个数组,你应该意识到